As Final Fantasy arrives in US cinemas, BBC News Online's entertainment correspondent Tom Brook looks at its impact on the future of cinema - and the careers of Hollywood's highest paid stars.

Final Fantasy: The Spirits Within, the first full-length feature with a cast made-up entirely of photo-realistic humans, has arrived in American cinemas.

Audiences at early screenings have been favourably impressed by the life-like array of computer generated characters that appear on screen.

This futuristic thriller, from director Hironobu Sakaguchi - creator of best-selling Final Fantasy videogame - boasts an illustrious collection of actors who supply just their voices.

I feel I have given birth with my voice to a character, this real human being - it's a little eerie

Actress Ming-Na, the voice of Aki Ross

But the hyper-real human creatures that appear on screen overshadow the collective vocal talents of Alec Baldwin, Donald Sutherland, James Woods and Steve Buscemi.

While some of the human looking creatures are noticeably synthetic, some are surprisingly authentic.

The film's star, a curvaceous heroine called Dr Aki Ross, is already real-looking enough to have become an object of desire.

Her bikini-clad computer generated image has graced the pages of Maxim, the men's magazine.

Time-consuming

Actress Ming-Na who gives Aki Ross her voice has been a little taken aback by how lifelike her character appears.

She says: "I feel I have given birth with my voice to a character, this real human being. It's a little eerie, a little surreal in some ways."

Digital artists worked for four years on the film

Aki Ross was just one of several human-looking characters created by a team of 200 digital artists who were engaged in the making of Final Fantasy.

The film represents the culmination of almost four years' work, costing well over $100m, undertaken by Hironobu Sakaguchi's Square Pictures to achieve state-of-the-art photo-real human characters.

Creating Aki Ross was itself a massive endeavour because computer software had to deployed to create more than 60,000 hairs in her head.

Also, to make the synthetic actors more real they were "imperfected" with acne, freckles and pores.

Aliens

The technology on display in Final Fantasy is far more inspiring than the story. The film, set in the year 2065, depicts the earth under siege from strange ghost-like alien forces.

Humans disagree on how best to combat the threat. Scientist Dr Aki Ross, aided by a band of renegades, fervently believes in a holistic New Age solution.

Alien forces attack Earth in Final Fantasy

The more villainous General Hein, whose voice comes from James Woods, favours a bold militaristic plan.

The dialogue dwells far too long on the intricacies of how these ghost-like alien forces operate.

The characters attempt to navigate the audience through needlessly complicated scenarios with laborious expositions of plot.

Clone

The arrival of a big budget film, distributed by a major Hollywood studio, with computer-generated human stars has definitely raised some anxieties.

Among some actors there is concern that these "synthespians" as they are called, will eventually replace humans.

The technology is still some way off from making this a real possibility.

Photo-realistic actors: Forever young

But nobody doubts that producers would employ compliant computer-generated actors who require no salary, and hardly any upkeep, if they thought they could get away with it.

Tom Hanks is concerned that technology will enable unscrupulous auteurs illegally to use a computer generated image of himself - or use a digital clone to tamper with his existing performances.

He told the New York Times this week that he was troubled by it. He said: "It's going to happen. And I'm not sure what actors can do about it."

In defence, supporters of computer-generated human characters say they are just tools that add to the film-makers palette and that actors have no need to fear.

They point out that the technology on display in Final Fantasy could give actors a new lease on life.

Youth

Alec Baldwin gives voice to Captain Gray Edwards in Final Fantasy, a handsome young hero who looks considerably younger than the middle-aged actor.

Baldwin, clearly pleased by the results, commented: "I don't have to look like Gray. They can make Gray perfect in every way that I am not perfect."

Final Fantasy: Great technology but poor story

Using the same technology, digital artists claim it will soon be possible to scan images of Baldwin from his early days as an actor, and then use these to synthesise a perpetually young computer-generated movie star.

The advent of a computer-generated human cast will also inevitably shift creative control of a motion picture towards the director.

In conventional film-making there is a creative collaboration between the actors and directors.

But in a film like Final Fantasy the director has absolute control over how the computer-generated actors use gestures to interpret the narrative.

In fact, some film industry figures find the advent of "synthespians" a deplorable trend. They worry that the public will ultimately suffer, not knowing, for instance, if a television newsreader is a real human being or a computer creation.

But supporters of the technology are fearless. Director Hironobu Sakaguchi, says the next stage is combining real humans with photo-realistic counterparts.

He says: "It would be very interesting to see these actors, who are created in a digital world, to be able to join scenes with real human actors."

Although Final Fantasy represents a major step forward with its synthetic human cast, it shows only the potential of this new technology.

The movie going public is still waiting to be transfixed by a compelling computer-generated human cast in a film that has an equally strong story to match.